---
title: Writing agent state
icon: "lucide/ArrowRight"
description: Write to agent's state from your application.
---

<video
  src="https://cdn.copilotkit.ai/docs/copilotkit/images/coagents/write-agent-state.mp4"
  className="rounded-lg shadow-xl"
  loop
  playsInline
  controls
  autoPlay
  muted
/>
<Callout>
  This video shows the result of `npx copilotkit@latest init` with the [implementation](#implementation) section applied to it!
</Callout>

## What is this?

This guide shows you how to write to your agent's state from your application.

## When should I use this?

You can use this when you want to provide the user with feedback about what your agent is doing, specifically
when your agent is calling tools. CopilotKit allows you to fully customize how these tools are rendered in the chat.

## Implementation

<Steps>
  <Step>
    ### Run and Connect Your Agent to CopilotKit

    You'll need to run your agent and connect it to CopilotKit before proceeding. If you haven't done so already,
    you can follow the instructions in the [Getting Started](/crewai-flows/quickstart) guide.

    If you don't already have an agent, you can use the [coagent starter](https://github.com/copilotkit/copilotkit/tree/main/examples/coagents-starter-crewai-flows) as a starting point
    as this guide uses it as a starting point.

  </Step>
  <Step>
    ### Define the Agent State
    CrewAI Flows are stateful. As you transition through the flow, that state is updated and available to the next function. For this example,
    let's assume that our agent state looks something like this.

    <Tabs groupId="language_crewai-flows_agent" items={["Python", "TypeScript"]} persist>
      <Tab value="Python">
        ```python title="agent.py"
        from copilotkit.crewai import CopilotKitState
        from typing import Literal

        class AgentState(CopilotKitState):
            language: Literal["english", "spanish"] = "english"
        ```
      </Tab>
    </Tabs>

  </Step>
  <Step>
    ### Call `setState` function from the `useCoAgent` hook
    `useCoAgent` returns a `setState` function that you can use to update the agent state. Calling this
    will update the agent state and trigger a rerender of anything that depends on the agent state.

    ```tsx title="ui/app/page.tsx"
    import { useCoAgent } from "@copilotkit/react-core"; // [!code highlight]

    // Define the agent state type, should match the actual state of your agent
    type AgentState = {
      language: "english" | "spanish";
    }

    // Example usage in a pseudo React component
    function YourMainContent() {
      const { state, setState } = useCoAgent<AgentState>({ // [!code highlight]
        name: "sample_agent",
        initialState: { language: "english" }  // optionally provide an initial state
      });

      // ...

      const toggleLanguage = () => {
        setState({ language: state.language === "english" ? "spanish" : "english" }); // [!code highlight]
      };

      // ...

      return (
        // style excluded for brevity
        <div>
          <h1>Your main content</h1>
          {/* [!code highlight:2] */}
          <p>Language: {state.language}</p>
          <button onClick={toggleLanguage}>Toggle Language</button>
        </div>
      );
    }
    ```

  </Step>
  <Step>
    ### Give it a try!
    You can now use the `setState` function to update the agent state and `state` to read it. Try toggling the language button
    and talking to your agent. You'll see the language change to match the agent's state.
  </Step>
</Steps>

## Advanced Usage

### Re-run the agent with a hint about what's changed

The new agent state will be used next time the agent runs.
If you want to re-run it manually, use the `run` argument on the `useCoAgent` hook.

The agent will be re-run, and it will get not only the latest updated state, but also a **hint** that can depend on the data delta between the previous and the current state.

```tsx title="ui/app/page.tsx"
import { useCoAgent } from "@copilotkit/react-core";
import { TextMessage, MessageRole } from "@copilotkit/runtime-client-gql";  // [!code highlight]

// ...

function YourMainContent() {
  // [!code word:run:1]
  const { state, setState, run } = useCoAgent<AgentState>({
    name: "sample_agent",
    initialState: { language: "english" }  // optionally provide an initial state
  });

  // setup to be called when some event in the app occurs
  const toggleLanguage = () => {
    const newLanguage = state.language === "english" ? "spanish" : "english";
    setState({ language: newLanguage });

    // re-run the agent and provide a hint about what's changed
    // [!code highlight:6]
    run(({ previousState, currentState }) => {
      return new TextMessage({
        role: MessageRole.User,
        content: `the language has been updated to ${currentState.language}`,
      });
    });
  };

  return (
    // ...
  );
}
```

### Intermediately Stream and Render Agent State

By default, the CrewAI Flow agent state will only update _between_ CrewAI Flow node transitions --
which means state updates will be discontinuous and delayed.

You likely want to render the agent state as it updates **continuously.**

See **[predictive state updates](/crewai-flows/shared-state/predictive-state-updates).**
